Currently, a typical example of a vertical take-off and landing aircraft capable of generating lift without running on the ground is a helicopter. A helicopter has a large rotor, compared with its fuselage, and generates lift and thrust by rotating the rotor. Also known as one of the few examples is a fixed-wing aircraft that performs vertical take-off and landing by deflecting thrust of a jet engine.
The fuselage of a helicopter is relatively large in itself, and in addition, the helicopter is equipped with a main rotor larger than its fuselage and a tail rotor at the tail of its fuselage. Thus, if take-off, landing or attitude control is performed in a small space surrounded by obstacles such as buildings or trees, the main rotor or the tail rotor may come into contact with the obstacles. Accordingly, a large space is needed for the take-off and landing.
In the case of a fixed-wing aircraft capable of vertical take-off and landing using a jet engine, the jet exhaust is high in temperature and also large in volume. Accordingly, small objects such as stones are blown off by the jet exhaust during take-off or landing, possibly damaging surrounding buildings or the like. Thus, also in the case of the fixed-wing aircraft, a large space is needed for the take-off and landing.
There have already been proposed vertical take-off and landing (VTOL) aircraft capable of safe take-off and landing even in a small space (see Patent Documents 1 and 2, for example). The vertical take-off and landing aircraft described in Patent Documents 1 and 2 are equipped with ducted fans having propeller type fans arranged within cylindrical ducts or nacelles.